During her tenure as the CIA’s top lawyer, Caroline Krass dealt with investigations into the CIA’s enhanced interrogation programs and black sites, unrest in Ukraine and Crimea, the rise of ISIS, normalizing relations with Cuba, the Syrian refugee crisis, and Russian meddling. Now headed out the door, she says the most challenging threat the United States faces comes from cyberspace.

“I think the hardest [legal questions] were those that surrounded cyber,” Krass said on Tuesday at an event at Georgetown University Law School. “It’s an evolving area of the law, trying to determine answers to questions like what constitutes a use of force…what are the measures to combat such a use of force?”

President Donald Trump ishoping to confirm a new top lawyer for the Central Intelligence Agency this week to replace Krass, who is stepping down after three years. She’d previously worked in the Department of Justice’s Office of Legal Counsel, the National Security Council, the State Department, and the Treasury.

Getting the legal lay of the land correct in cyberspace is still on Washington’s to-do list, even though think tanks and experts have spent years arguing about what the rules of the road for cyberspace might look like. Washington, for example, has no formal definitions for cyber warfare or any clear standards for how to retaliate for cyber attacks. When the United States pointed the finger at North Korea for a massive hack on Sony Pictures in 2015, President Barack Obama slapped sanctions on Pyongyang in response; but the United States has yet to reach a decision about how to respond to alleged Russian state hacking that interfered in the 2016 U.S. presidential election.

And, knowing what she knows now, Krass says digital attacks are the biggest threat the country will face in the future. “It’s constantly evolving, it’s unknown. It’s at the intersection between what both state actors and non-state actors can do…to harm vital systems within our country,” she said, citing potential targets like critical infrastructure and financial systems. “I think it’s a real concern.”

Worrying about cyberspace is a departure from how Krass started her tenure in 2014, in the midst of multiple investigations into the CIA’s enhanced interrogation programs. Krass argued that the later Senate Intelligence Committee report — which denounced the program — was “one-sided.” But, she said, “The agency has admitted mistakes were made.”

Trump’s position on torture is still not entirely clear: He embraced it on the campaign trail, then seemed to disown the practice when Gen. James Mattis, his defense secretary, told him it doesn’t work. Krass said the CIA’s lawyers are bound to prevent that torture from recurring unless Congress changes the law, which outlawed the practice in 2015.

“That is the law of the land and they’ll be sure to follow it,” she said. She also told the audience there is a team of around 150 attorneys in the CIA’s legal shop who will be remaining in their positions, which is a good thing because CIA lawyers are likely to get busier.

Earlier in April, newly-minted CIA head Mike Pompeo thrashed notorious transparency website Wikileaks and its publisher Julian Assange for dumping a trove of documents detailing the CIA’s hacking tools. Now, the Department of Justice is reportedly considering charging Assange with a crime for his decision to post the documents. It’s unclear what specific crimes it would charge him with, but many are concerned a witch hunt for Assange could threaten First Amendment rights.

Asked what advice she’d give to her successors on pursuing charges against Assange, Krass said “you do need to be careful to safeguard the interests of the free press…but there are also situations where charges may be appropriate.”

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Jenna McLaughlin is Foreign Policy's intelligence reporter. You can reach her on Signal at 203-537-3949. @JennaMC_Laugh